Beryllium-gold alloy and article made therefrom



B. BRENNER Sept. 13, 1966 BERYLLIUM-GOLD ALLOY AND ARTICLE MADETHEREFROM Filed Oct. 18, 1965 O m m w O L V 9 W H w W m o 1 M 8 W M o m7 m w m w N N M M w m W w A O m J 4 mm 0 3 D? f W m m l m n w m w w a wM m x a a m m m m a 4 0 OOO mufi; IOZ MVEDGW Eun- WOZDOQ 7: Ikozwmkw wzmzmh R E N mm mm. WT R E B Y B BERYLLIUM CONTENT IN PARTS PER MILLIONTIMES IO, BALANCE GOLD ATTORNEY United States Patent 3,272,625BERYLLlUM-GOLD ALLOY AND ARTICLE MADE THEREFROM Bert Brenner, Tenafly,N.J., assignor to James Cohn, White Plains, N.Y., and Richard Cohn,Scarsdale, N.Y., jointly Filed Oct. 18, 1965, Ser. No. 502,763 2 Claims.(Cl. 75--165) This application is a continuation-in-part of myapplication Serial No. 283,455, filed May 27, 1963, now abandoned.

This invention relates to the art of alloys generally and, moreparticularly, to a beryllium-gold alloy having improved physicalproperties and to an article made of such alloy.

In the ensuing discussion and in the appended claims the term gold,unless otherwise qualified, is understood to mean gold of highcommercial purity.

The alloy of this invention has wide application. It is especiallyuseful in various branches of the electrical industry which employ goldin different forms, including fine wire, as the material of a variety ofelectrically conductive elements. The alloy may, for example, beadvantageously employed as the material of certain electricallyconductive elements in semiconductor devices and in otherinstrumentalities which require that such elements comprisesubstantially pure gold, i.e. in the neighborhood of 99.99% gold.

While gold is considered as being a ductile metal, this is true only indiameters of about 0.002 and greater. As is well knOWn in the art, it isvery difficult and quite expensive to draw gold wires in diameters of0.002 and smaller. One reason for this is that gold has low tensilestrength and, as a consequence, unless great care is exercised,relatively fine diameter gold wire pulls apart in the dies instead ofbeing properly drawn therethrough. Also, gold in smaller diameters selfanneals at ordinary room temperatures. Such gold is, therefore, unstableand is extremely difiicult to draw.

Considerable research has been carried out in recent years with the viewof explaining this undesirable characteristic of gold. It is now thoughtthat lattice distortion due to dislocations, voids or other defects inthe crystal lattice is the probable and likely cause for thisundesirable characteristic of gold in fine wire form.

I have discovered that the addition of extremely small or minute amountsof beryllium to gold has the surprising, unexpected and highly desirableand beneficial effects of (1) increasing the tensile strength to a greatextent, (2) substantially improving the ductility of gold in fine wireform and (3) rendering the gold stable. Hence, a beryllium-gold alloyaccording to this invention affords a relatively high purity gold whichis both ductile and stable and which may be formed more readily andeconomically into fine wire than gold that does not contain beryllium inthe amounts indicated above and identified more particularlyhereinafter.

It is the primary object of this invention to provide substantially puregold having improved properties.

Another object of this invention is to increase the tensile strength andimprove the ductility of gold.

A further object of this invention is to provide an alloy, consistingessentially of a minute amount of beryllium and the balance gold, whichalloy has improved physical properties, such as high tensile strengthand better ductility, as compared to gold compositions which do notcontain beryllium in such amount.

A still further object of the invention is to provide a beryllium-goldalloy which may be readily and economically produced, such as bydrawing, into long lengths of relatively fine diameter wire.

3,272,625 Patented Sept. 13, 1966 The enumerated objects and additionalobjects, together with the advantages of the invention, will be readilycomprehended by persons trained in the art from the detailed descriptionthat follows taken in conjunction with the annexed drawing which is agraph containing two curves that were obtained by plotting the tensilestrength of annealed elements and hard drawn elements made of alloysaccording to this invention against the beryllium-gold content of suchalloys.

Since it is well known that the tensile strength of a wire of any givenalloy is affected by both the heat treatment of the final wire and theamount of working or drawing it has received, as well as by thecomposition of the alloy, it is understood that the two curves in theaccompanying graph, marked A and B, represent the extremes which may beobtained for any given composition. In other words the area betweencurve A and curve B represents the characteristics of wire obtained byemploying the present invention.

It is recognized that the use of beryllium as a hardening agent forcertain metals, other than gold, is well known to the art. In suchinstances, the beryllium component usually constitutes several weightpercent of the resultant alloy. For example, it has long been known toemploy beryllium as a hardening agent for copper. The amount ofberyllium contained in commercial beryllium-copper alloys is usually inthe range of from 2% to 2.5%. The hardening effect of beryllium oncopper is understood to be due to precipitation hardening. Thishardening effect of beryllium on copper is largely latent and cannot befully attained until the beryllium-copper alloy is subjected toelaborate heat treatment.

Attempts to increase the tensile strength of gold by the addition ofseveral weight percent of beryllium, such as from 2% to 2.5%, the amountgenerally used on commercial beryllium-copper alloys, have all resultedin complete failure. Moreover, experimentation has demonstrated thatalloys containing as little as 1% beryllium and the balance gold areundesirably brittle and are unsuited for the production of wire.

It has been ascertained that the objectives of this invention aresuccessfully attained by beryllium-gold alloys consisting essentially ofberyllium in the amount of 0.001% to 0.1% by weight and the balancegold. Alloys consisting essentially of beryllium in an amount greaterthan about 0.1% and the balance gold are considered unsuitable as theytend to become brittle and cannot be readily drawn or otherwise formedinto a fine wire having a diameter less than 0.002.

Preferred and recommended beryllium-gold alloys of this inventionconsist of beryllium in the amount of 0.0025% to 0.0075% by weight andthe balance gold. These alloys permit the fabrication of fine,electrically conductive gold elements hardened with beryllium in apurity better than 99.99% gold which is the commercially acceptedstandard for pure gold elements in many electrical applications.

It will be appreciated from an examination of the curves appearing onthe graph that the addition of beryllium in the amounts specified aboveto gold greatly increases the tensile strength, whether elements madetherefrom are annealed, as represented by curve A, or hard drawn, asrepresented by curve B, or whether they lie between these two extremes.

Referring first to curve A, it will be noted that annealed gold has atensile strength of approximately 17,200 pounds per square inch. Bysubstituting minute amounts of beryllium, i.e. up to 0.1% beryllium, fora like amount of gold, the tensile strength of the resultant alloy israised to approximately 28,000 pounds per square inch. This constitutesan increase of almost 63% in tensile strength.

Referring now to curve B, it will be observed that hard drawn gold has atensile strength of approximately 38,000 pounds per square inch. Byagain substituting up to 0.1% beryllium for a like amount of gold, thetensile strength of the resultant alloy is raised to approximately76,000 pounds per square inch. This constitutes a 100% increase intensile strength.

The same observations obviously apply to any intermediate tempers of thewire between the two extremes shown in curves A and B. The tensilestrength range of any alloy within the composition limits, and alsothose of pure gold, can easily be read off from the graph.

It will be noted from the graph that a wire according to this inventionand consisting essentially of beryllium in the amount of about 0.001% toabout 0.1% by weight and the balance gold has a tensile strength withinthe range of about 18,000 pounds per square inch and about 76,000 poundsper square inch. It will also be noted that such a wire, consistingessentially of beryllium in the amount of about 0.0025% to about 0.0075%by weight and the balance gold, has a tensile strength within the rangeof about 20,000 pounds per square inch to about 57,000 pounds per squareinch.

From the foregoing, it is believed that the objects,

advantages and utility of the present invention will be readilycomprehended by persons skilled in the art without further description.It is to be clearly understood that all matter contained in the abovedescription or shown in the drawing is to be interpreted as illustrativeand not in a limiting sense.

Iclaim:

1. A wire having a diameter less than 0.002 inch and made of an alloyconsisting essentially of beryllium in the amount of about 0.001% toabout 0.1% by weight and the balance gold, said wire having a tensilestrength within the range of about 18,000 pounds per square inch toabout 76,000 pounds per square inch.

2. A wire having a diameter less than 0.002 inch and made of an alloyconsisting essentially of beryllium in the amount of about 0.0025% toabout 0.0075% by weight and the balance gold, said wire having a tensilestrength within the range of about 20,000 pounds per square inch toabout 57,000 pounds per square inch.

No references cited.

DAVID L. RECK, Primary Examiner.

C. N. LOVELL, Assistant Examiner.

1. A WIRE HAVING A DIAMETER LESS THAN 0.002 INCH AND MADE OF AN ALLOYCONSISTING ESSENTIALLY OF BERYLLIUM IN THE AMOUNT OF ABOUT 0.001% TOABOUT 0.1% BY WEIGHT AND THE BALANCE GOLD, SAID WIRE HAVING A TENSILESTRENGTH WITHIN THE RANGE OF ABOUT 18.000 POUNDS PER SQUARE INCH TOABOUT 76,000 POUNDS PER SQUARE INCH.